Fire control system



KR 294139573 1 I, w .W -R I 7 y Dec. 31, 1946. E. E. LIBMAN 2,413,573

FIRE CONTROL SYSTEM Filed Aug. 21, 1944 s Shets-Sheet 1 Fig l x Vt COST INVENTOR.

-- '54RL L/BMAN" ATTORNEY Dec. 31, 194-6. B

FIRE CONTROL SYSTEM Filed Aug. 21, 1944 3 Sheets-Sheet 3 INVENTOR. EARL E Ll BMAN ATTORNEY Patented Dec. 31, 1946 FIRE CONTROL SYSTEM Earl E. Libman, Brooklyn, N. Y., assignor to Control Instrument Company, Inc., Brooklyn, N. Y., a corporation of New York Application August 2.1, 1944, Serial No. 550,466

This invention relates to improvements in fire control systems and has particular reference to a computer and method of operation especially adapted for use in surface fire from a moving ship to a moving target.

It is proposed, by the present invention, to obtain improved accuracy of fire by manually setting in the instrument the own ship and target speeds, the relative target bearing and target angle, the range, and the wind velocity and hearing, and to read the values of sight angle and sight deflection resulting when the said various inputs have been introduced in the instrument, said values being then set in the gun sights, with the addition of spot corrections if desired. While fire control instruments have been heretofore designed for somewhat similar purposes, they have been highly complicated and costly mechanisms, which are not portable and are incapable of use by other than highly trained personnel.

Accordingly, an object of the invention is to provide an improved fire control system of comparatively simple and inexpensive construction, employing calculating elements and associated mechanisms capable of easy assembly and adjustment in a very compact, light and portable computer, and wherein no backlash or lost motion will develop in any of the essential calculating elements or their operating mechanisms.

Another object is to replace the complicated calculating mechanisms usually employed by providing in lieu thereof, novel forms of charts and curves which greatly simplify the computations, so that they will not be difficult to read or understand, thus enabling the instrument to be conveniently operated by personnel having less experience than that usually required for fire con trol instruments of known types.

Another object is to provide for the addition of spot corrections in sight deflection and in range without disturbing the other settings of th instrument.

A further object is to maintain extreme accuracy in the instrument without the use of ac- -eurately mechined parts or tedious and difficult adjustments. Such accuracy is obtained by the novel arrangement and control of charts provided in the instrument, and is determined primarily by the accuracy of the input quantities set in the instrument, rather than by any limitations established by the instrument itself.

The above and other objects will appear more clearly from the following detailed description when taken in connection with the accompanying drawings, which illustrate a preferred em- 6 Claims. (Cl. 235-615) .bodiment-of the inventive idea; but it is to be expressly understood that said drawings are employed only for the purpose of describing the invention as a whole and not to define the limits thereof, reference being had to the appended claims for this purpose.

In the drawings:

Fig. 1 is a diagrammatic view illustrating the method of resolving the components of motion in the fire control problem.

Fig. 2 is a similar view illustrating the present position of the target relative to the own ship.

Fig. 3 is a diagrammatic view illustrating the resolution of the wind correction to be applied.

Fig. 4.is a view illustrating the method of constructing a chart giving sight deflection as a function of average shell velocity and bearing rate.

Fig. 5 is a plan view of a wind correction chart employed in connection with the invention.

Fig. 6 is a fragmentary plan view of a chart displaying present range, and used to produce average shell velocity.

Fig. '7 is a fragmentary plan view of a chart displaying sight angle as a function of average shell velocity.

Fig. 8 is a plan view of a chart displaying spot corrections in range, and

Fig. 9 is a schematic diagram in perspective showing all the essential features of the invention.

To aid in a complete understanding of the invention, the method of mathematically establishing the procedure of calculating sight angle and sight deflection from the given inputs of relative target bearing, own ship speed, target angle, target speed, present range, wind bearing and wind velocity, will first be explained. These quantities will be defined by reference to Figs. 1 to 3, and, as will be seen, the mathematical relationship derived will permit. the solution of the fire control problem by the use of simple charts, rather than by the usual expensive and The methods employed in constructing the charts based on these mathematical relationships will be next explained by reference to Figs. 4 to 8, and finally the method of utilizing the charts in the complete invention will be illustrated by Fig.9.

In Fig. l, the own ship is proceeding at a speed of V0 knots. The position of the target relative to the own ship is indicated by the relative target bearing B and'the present range R. The target is proceeding at a speed Vt and the target angle is 1'. The angles B and -r are measured clockwise from the bows of the ship to the line of sight. The components of relative speed between the own ship and the target are found by resolving the speed of each ship into components along the line of sight and across the line of sight. Addition of these components with the proper signs will give the range rate and the linear bearing rate.

Range rate R will be assumed positive when the range is increasing. The compass bearing 30 of the target is equal to B plus own ships course, designated by CS0. The linear bearing rate RBc will be assumed positive when the target is apparently moving toward the right, that is, when the line of sight is rotating clockwise as viewed from the own ship.

Expressing V and Vt in yards per second and expressing the time rate of change of any quantity by placing a dot over the character designating it, the range rate is (1) R=V0 cos BVt cos 1' The linear bearing rate is (2) RBc=vo sin B-i-Vt sin 1 Fig. 2 illustrates the method of solution of the problem. The own ship and target are respectively at positions 0 and T when the gun is fired. the intervening present range being R. V is the velocity of the target relative to the own ship, and has components R and R130 which are measured respectively along and perpendicular to the line of sight. During the time of flight Ta. of the shell,

the apparent relative motion of the target will cause it to move to some position T. Triangles I and 2 are similar, the sides of triangle 2 being, respectively, Ta times as large as the sides of triangle I. It is required to find the sight deflection D between the line of sight and the line of fire, and the sight angle or angle of elevation of the gun above the horizontal at the advance range Ra. From Fig. 2 it is seen that (3) Ra sin D=RBcTa 4 R11 cos D=R+RTa Since the sight deflection D does not ordinarily reach a value of more than about six degrees, cos D may be assumed equal to unity without introducing appreciable error. Designating the average velocity of the shell over its trajectory by m, and putting cos D equal to unity, these become:

the cross wind component is seen to be given by the expression W sin (Bw) If D is the corrected deflection,

D'=D+wa where w is the cross wind correction and 5 the drift correction, expressed as angular corrections to the deflection D. Drift correction is obtained from a standard U. S. Navy data table and as the drift is always to the right, its correction is always subtracted, hence 6.

Since w5 does not exceed 2.8, its cosine can be assumed equal to unity, and its sine equal to the angle. As cos D has also been assumed equal to unity,

If u is the angular correction for cross wind of unity velocity, uW sin (Bw) is the correction for wind of velocity W sin (B-w) and thus Sin D,=12% muW sin (Bw) where for brevity $==RBc+muW sin (Bw) ma.

The method of employing the equations in the mechanism can now be indicated. By resolving tse own ships and targets speed along and perpendicular to the line of sight by means of resolvers and adding the components appropriately, R and R30 can be obtained from Equations 1 and 2.

Since Ta depends upon m, the R and R thus determined can be employed to find m from (6).

As previously described, m is defined as being equal to Ra/Ta. The standard U. S. Navy range tables for surface guns list the corresponding values of Ra and Ta. By dividing each Ra by its corresponding Ta, there is obtained the corresponding m and from this a table may be formed having values of Ta corresponding to m for a gun having a, specific known muzzle velocity. Thus, if m is known, To is known and is a function of m and Equation 6 may be written as Therefore, only R, R and m are involved in said equation and so, for any pair of R and R, the value of m is determined and can be calculated. Having the value of m, the observed value of the wind velocity and of the wind direction, the quantity muW sin (Bw) can be obtained. The quantity m6 can also be determined from m. Thus all the quantities in ('7) are determined and the value of the corrected sight deflection D can be found. As sight angle is a function of range or of m, it can be found from m.

Differentiating the equation,

z M s Bs jmmss .1 n ives cos D AD m Since D is never greater than about 8, cos D can be assumed equal to unity, which will reduce the equation to This equation may be used to establish a meth-' d of adding spot corrections to sight deflection. An increase in D to D+AD' can be expressed as I s sin (D'+AD) AD lies between :25 mils or :1.5 and its cosine lies between 10.9997 and, for purposes of the present invention, is taken (with very small error) to be unity and, therefore, with a high degree of accuracy, AD may be assumed equal to the sin AD. Thus to add the spot correction AD, the quantity mAD is added to 0:.

To add a spot correction ARa to the advance range Ra, it is necessary only to select a value of sight angle which corresponds to Ra+ARa, or to m+Am, Where Am is the change in m corresponding to ARa. Since m by definition is Ra/Ta and Ta itself depends on Ra, so does m=Ta/Ra and Ra depends on m or the quantity Ra is a function of m, or Ra=F1 (m) andAlga=Ffl m) Am ARa Am- 20 Thus, sight angle at Ra-l-AR may be expressed as i" (9) Sight angle F- Fawn.)

It is evident that ('7) can be written as ar=m sin D which for given values of D is the equation of a straight line passing through the origin of a set of axes along which :r and m are measured. This is illustrated in Fig. 4, where these straight lines are plotted for various values of D marked on the lines. Thus for any pair of values of m and a: which are computed from the given data and the chart moved to the corresponding position, the sight deflection D can be read from the curve to which the pair corresponds.

From standard range tables the values of unit wind correction u can be obtained for various values of m and corresponding values of am may be calculated. At a given wind velocity W, the quantity muW will depend upon W and m, and if curves are plotted of the quantity 7=muW for various values of Y against axes W and m, the curves of Fig. 5 are obtained. The values of or muW are shown on the curves. Since the curves are multiples of each other, the chart Fig. 5 is essentially a multiplying device, from which multiple values of muW can be read.

Since 112. and Ta are related or dependent quantities in the Equation 6 trates a chart or tape on which sight angle is shown as a function of m. The equation for range spot correction indicates that curves may be plotted of various values of ARa against aXes of Am and F2(m). Fig. 8 is a-chart giving curves of ARa a a f tion of m and Am,

The equation for spot correction in sight deflection Ax=mAD is in the same form as cv=m sin D which was represented by Fig, 4, and therefore can be shown on a similar chart.

Referring to Fig. 9, the numerals II and I2 indicate graduated dials of own ship and target resolvers, respectively, between which extends the line of sight I3. In order to set in the iven relative target bearing data on the peripheral degree scale of the dial I I, a knob I4 on the panel of the instrument is connected to said dial by the gear I5. A second scale I6 radially arranged on the dial II is graduated in knots of ships speed with 0 speed at the center of the dial. For the purpose of setting in the target angle 1' in the target resolver, the dial I2, also having a circular degree scale, is rotated by means of a gear I I operated by the knob I8. Said dial I 2 is also provided with a radial scale I9 similar to the scale 16.

. .Associated with own ship dial II and arranged above the same are two overlapping strips and 2I of transparent material, having, respectively, the cross hairs 22 and 23. The strip 20 is arranged parallel to the line of sight I3, while the strip 2| is disposed across the line of sight and at right angles to the strip 20. One end of the strip 20 is fixed to a follower nut 24 through which extends a screw 25 geared to a handle 26, so as to move the nut; 24 along the screw and thus adjust the strip 20 when said handle is rotated. Similarly, the strip 2I is carried by the follower nut 21 mounted on the screw 28 geared to the handle 29. After the dial II has been adjusted to indicate the relative target bearing, the own ship velocity is indicated on the scale I6 by adjusting the two strips 20, H by amounts equal to the own ship's components of speed across the line of sight and in the line of sight, until the cross hairs 22. 23 intersect on said scale at the given value of the own ship's speed. Like the dial I I, the dial I2 also has associated therewith transparent strips 30 and 3| carried, respectively, by the follower nuts 32 and 33 mounted on the screws 34 and 35, with the former geared to the handle 36 and the latter to the handle 37. Thus,

after the dial I2 has been set to the given target angle 1', the overlapping strips 30, 3I are adjusted until their respective crosshairs 38, 39 intersect on the scale I 9 at the given target speed, said target angle and speed being obtained by observation and the employment of standard'means for estimating the same. As with the own ship dial II, said cross hairs move by amounts which are equal to the components of motion of the target in the line of sight and at right angles thereto.

The components of own ship and target speeds in the line of sight efiected by the adjustments above described, are added or combined in order to obtain the range rate R. To accomplish this,

a flexible element 40 in the form of a steel tape,-

wire, or the like, has its ends secured to the follower nuts 27 and 33, and its intermediate portion is extended around a fixed idler pulley 4| and a m r hlapuney theshaitiii of much i ar e the motions of said follower nuts 21, 33, These motions imparted to the transparent strip 41 represent the range rate R which will be employed in the calculation of future or advance range and average shell velocity to be obtained from the chart 48 (Fig. 6) over which the strip 41 is adjustable. Said chart is movably mounted upon an adjusting unit consisting of upper and lower pairs of rollers 49, 50, and 52, respectively, with the ends of the chart extended around the lower rollers and the intermediate portion extended over the upper rollers so that the chart will be rolled up on one or the other rollers in accordance with the direction of rotation of the drive roller 49, which carries sprocket teeth 53 at each end engageable in openings formed in the edges of the chart. Said chart is maintained taut on said rollers by a constant tension exerted on the roller 5| by a spring 54 coiled on the shaft of said roller. Said spring is interposed between and has its ends joined to the roller 5| and a gear 55 loose on said shaft. The gear 55 is connected to a similar gear 56 on the shaft of the roller 52 by means of an idler 51. During assembly of the unit, the chart 48 is placed in position on the rollers, and with idler 51 disconnected from the gear 55 and with the rollers 5|, 52 held stationary, said gear 55 is turned to place the spring 54 under tension. The idler 51 is then engaged with the gears 55, 56, and due to the torque exerted by the spring 54, a tension will be maintained on the chart 48. Since the gears 55, 56 must rotate by the same amount, this tension will remain substantially constant, regardless of the position to which the chart may be adjusted.

The handle 58 provides the input for present range by means of which the average shell velocity m for a given adyance range is established. Said handle is geared to the shaft 59 which, through the gear 60 thereon, drives the gears SI and 52 on the shaft 63, and further drives the gears 64 and 65 on the shaft 66. Said shaft 66 extends through the differential assembly indicated by the differential spider gear 61. Said gear 65 drives the roller 49 through the two idler gears 68, so that a turning movement of the shaft 59 in either direction will be transmitted to the roller 49, whereby the chart 48 will be transferred from the roller 5| to the roller 52, or vice versa, and thus moved relative to the cross hair 41 on the transparent strip 41.

Thus the inputs to the range chart are the present range introduced into the instrument by operation of the handle 58, and the range rate R which is set in by the operation of the own ship and target resolvers. When said resolvers are set in the machine by setting V0, B, Vt and T, the value R is computed by Equation 1 and fed into the chart representing Equation 6. Turning the m handle 58 until the index covers the value of R (known from the ran e finder on board ship) determines m and positions the m shaft. Thus by (6) the average shell velocity m for the given advance range is established as a rotation of the shaft 59 which positions the drift cam 69, the drum 14 on which is mounted the sight deflection spot chart 14', the range spot drum and the wind correction drum 16, as follows: The worm gear 12 on shaft 59 engages with the worm wheel '13 attached to the cam 69. The gear 11 on shaft 59 drives gear 18 and worm 19 on shaft 80, the said worm 19 in turn engaging gear 8| to drive the sight deflection spot drum mounted on shaft 82. Gear 83 on said shaft 82 engages with gear 84 on shaft 85 to rotate the attached drum 15 on 8 which is mounted the range spot chart 15'. Worm 86 mounted on said shaft engages with gear 81 on shaft 89 to drive the attached wind correction drum 16.

The range spot chart 15' described with reference to Fig. 8 is wrapped on the range spot drum 15, the m axis extending circumferentially around the said drum. Thus rotation of the said drum in accordance with the given value of m will bring the said chart to the correct position under the axially movable cross hair 90, which is carried upon and moved by the nonela tic wire or tape 9|. One end of said tape 9| is attached to the clock spring unit 92, which tends to rotate in the direction shown, thereby producing tension in said tape. From said spring unit 92, said tape 9| is led successively over idler pulleys 93, 94, 95 and 96 and is wrapped upon pulley 91. Gear 98 is attached to said pulley 91, and meshes with gear 99. The handle I00 and the pulley I03 are attached to said gear 99. Rotation of the said handle I00 will therefore rotate the pulley 91 through the gears 98 and 99. Rotation of the said pulley 91 will move the said cross hair axially along the drum 15, with or against the tension exerted by spring unit 92. Thus the positioning of the cross hair over the chart 15' to any desired value of range spot AM, as indicated in the description with reference to Fig. 8, may be produced by an appropriate manipulation of the handle I00.

The rotation of the pulley I03 and of the attached tape IOI is therefore a measure of & 20") and will be added to m, in a manner to be described, in order that the proper sight angle may be indicated as corresponding to m+Am or to the range+range spot. The said tape IOI is led from pulley I93 over idler pulley I02 and is attached to pulley I04. The clock spring unit I05, pulley I04, and pinion I08 are mounted on a sleeve I01, which is free to rotate on shaft 66. Tension is maintained in the tape ml by the spring unit I05, which tends to rotate the said sleeve assembly in the direction shown by the arrow. The tension in the tape II]! will balance the tension in the tape 9|, through the geared pulleys I03 and 91, and thus any tendency for the handle I00 to rotate from the tape tension will be eliminated. The internal gear I09 is attached to and rotates with shaft 56. The two pinions I08 rotate freely on shafts attached to gear 61, and mesh with both the said internal gear I09 and the pinion I06. This gear structure constitutes one form of the well known spur gear differential, having two inputs represented by the rotation of sleeve I01 and the rotation of the internal gear I 09, and an output equal to the rotation of gear 61, said output being equal to the sum of said inputs, or as previously described, to m-I-Am. Said output of gear 61 drives the sight angle chart II, illustrated by Fig. 7 through the two idler gears H0, The structure, method of mounting, and the oper- Y .ation 0f the chart III are in general identical with those described with reference to the present range chart 48. Thus values of sight angle corresponding to m+Am, or to advance range plus range spot, may be read from the said chart II I, with reference to the stationary index I I2.

As previously described, rotation of the handle 58 is employed to set in the average shell velocity m on the shaft 59. Said shaft 59 drives shaft 53 through gears 60 and BI. Gear H3 is attached to shaft 63, and drives the idler'gear II4 which in turn drives the rack II 5. The transparent strip II6 carrying the cross hair H1 is attached to rack H5, and i thereby adjusted in position over the sight deflection chart H8. The structure and method of mounting of the said chart H8 are identical with those described with reference to the present range chart 48. However, the drive roller I I9 is mounted on shaft I20, which carries the pulley I2I and the torsion spring 122. The non-elastic wire or tape I23 is attached to and wrapped on the said pulley I2I. Said torsion spring I22 is arranged to apply a torsional reaction to the said pulley I 2I, in the direction of the adjacent arrow, and will therefore maintain tension in the tape I23. The release or the pulling of the tape I23 will therefore rotate the pulley I2I to drive the chart II8 with or against the torsion spring I22.

From Equations 2, 7, and 8 it appears that As has been previously described, the values of (D'+AD') can be read from the chart of Fig. 4, corresponding to chart H8, at given values of (ZB-I-AT) and m, where (:r+A:l:) can be considered as the numerator of the above equation. It is therefore necessary to position the chart H8, or to operate the tape I23 in accordance with the numerator of said equation, and to position the cross hair III as described in order that the values of corrected sight deflection D or D'+AD' may be read on the chart II8. shown how each of the various quantities in said numerator can be derived from the mechanism and additively introduced as the motion of the tape I23.

The drift cam follower II is pivoted at I and is operated by the cam 69 through an angle which correspond to m6. One end of the tape I23 is attached to the free end of the follower II, and therefore moves a corresponding distance m5.

As previously mentioned, the equation for spot correction in sight deflection is Ax=mAD', the corresponding chart consisting of a series of straight lines with a common point of origin. The sight deflection spot drum I4 has wrapped upon it a chart similar in construction to that illustrated by Fig. 4, with the 'm. axis extending in a circumferential direction around the drum. The transparent strip I25, carrying the cross hair I24, is located above the said drum I4. The handle I28 is geared to lead screw I21, which moves the traveling nut I26 on which said strip I25 is mounted, thu permitting the movement of the cross hair I24 along the drum I4. After the said drum I4 has been positioned in accordance with the quantity m, the handle I28 is operated to move the cross hair I24 over the chart to the line designating the appropriate spot correction AD. The movement of the cross hair I24 is then the required Am. The pulley I29, attached to the underside of the traveling nut I 28,

is moved an equal amount. The tape I23 passes over the stationary guide pulley I30, the said movable pulley I29 and then over the stationary guide pulley I3I. The movement A0: of the said pulley I29 will therefore cause a proportional change in the length of the tape I23 looped around it.

The gear I which positions the own ship dial II is also geared to drive the dial I32. The index I33 is placed at the edge of dial I32, and is arranged to move in synchronism with the bow of It will now be the own ship dial, so that the angle B is represented between the index I33 and a vertical line through the dial center. The dial I34 is mounted on the sleeve I35, concentric with dial I32, and is driven from knob I36 through gears I31, I38 and I39. Said dial I34 is graduated circumferentially in degrees, and also has a radial scale of wind correction muW, with zero wind correction at the dial center. In operation of the said dial I34, the relative direction w of the apparent wind is set in on the dial I34 with respect to the previously adjusted index I33. The angle 3-21) is therefore represented between the radial scale of muW and the vertical line through the dial center.

The wind correction drum I6, which is rotated by the quantity m, has a chart I6 represented by Fig. 5 wrapped on it, with the m axis extending in a circumferential direction around the drum. A linear scale I40 of wind velocity W in knots is placed adjacent to the drum 16. After the drum I5 has been properly positioned in accordance with the quantity m, the wind correction muW can be read from the chart at any given valued wind velocity W.

The handle I44 is geared to the lead screw I45, which moves the traveling nut I45. The transparent strip I43, carrying the cross hair I42, is disposed above the dial I34, and is attached to the said traveling nut I46. Movement of the handle I44 therefore permits the cross hair I42 to be positioned at the value of muW on the radial scale I4l, as read from the wind correction chart I6.

As indicated, the traveling nut I46 and its attached pulley I4I, are then displaced by the amount of muW sin (B-w). The tape I23 is guided over the fixed idler pulley I48 and is then looped over the movable pulley I4I, causing any displacement of said pulley I41 to produce a proportional movement of tape I23. Said tape I23 is then looped around the movable pulley I50 attached to the traveling nut 24 to impart the own ships component of motion V0 sin B across the line of sight, to the movement of tape I23, the movement of the said traveling nut 24 being previously described with reference to dial II. Said tape I23 is next guided in turn over the fixed idler pulleys I49 and I5I, the movable pulley I52 attached to the traveling nut,

32, the idler pulley I53, and is attached to the drive pulley I2I. As described with reference to dial I 2, the movement of the traveling nut 32 is the target's component of motion Vt sin 7' across the line of sight, which is thereby added to the motion of tape I23. Thus all the various quantities V0 sin B+Vt sin 1+muW sin (B-w) m6+mAD are imparted additively to the motion of the tape I23, and the sight deflection corresponding to this motion and to the quantity m, can be read from the sight deflection chart I I8.

The operation of the instrument may be briefly summarized as follows:

w lSet thepwn ship dial lLtoAthe relativewtarl A get bearing B, which moves the index I33 on dial I32 to an equal angle.

2. Set the vertical and horizontal own ships cross hairs 22 and 23 to intersect at own ship speed, giving the component in the line of sight V0 cos B and the component across the line of sight V0 sin B.

3. Set the target dial I2 to the target angle 1.

4. Set the vertical and horizontal target cross hairs 38 and 39 to intersect at target speed,

giving the component in the line of sight Vt cos 1- and the component across the line of sight Vt sin -r.

5. Set present range on the range chart. This positions the shaft 59, which drives the sight deflection cross hairs I I1, the sight angle chart I I2, the drift cam 69, the wind correction drum "I6, the sight deflection spot drum I4, and the range spot drum 15. g

6. Set the dial I34 to the apparent direction 10 of the relative wind W with reference to the index I33 on the dial I32.

7. Read the value of muW on the wind correction chart 16', corresponding to the observed value of wind velocity W, and set the cross hair I42 on the radial wind dial scale MI.

8. Set the cross hairs 90 to the desired spot AR in range on the range spot chart I5.

9. Set the cross hairs I24 to the desired spot AD in sight deflection on the sight deflection spot chart M.

10. Read sight angle on chart III and sight deflection on chart H8.

As the mechanism of the instrument is required to drive only charts and dials, its construction may be very light, and does not require the use of ball bearings except in the pulley system which controls the sight deflection tape I23. It will be noted that none of the usual calculating elements are used, the calculations being performed by the use of charts. Great accuracy and facility in reading the charts may be secured by lengthening the charts to any suitable degree. This involves only appropriate changes in the gear ratios and does not increase the weight or cost of the instrument.

While one form of the invention has been described, it will be appreciated that various modifications can be made in the embodiment, arrangement, and application of the various principles described to the problem of gun fire control. The same mathematical formulae may be solved by equivalent calculating elements, as for example, by substituting mechanical calculating devices for charts and curves, in the event it is desired to employ automatic inputs or outputs. The systems of tape and pulleys employed for the addition and the conveyance of quantities involved in the calculations is especially subject to wide modifications. The scope of the invention is therefore not to be limited except as indicated by the following claims.

What is claimed is:

1. In a fire control system, mechanisms to obtain the components of own ship and target speeds in the line of sight including follower members, a transmitting mechanism including a fixed and a movable pulley, a flexible element extending around said pulleys and having its ends connected to said follower members so as to be operable thereby to move said movable pulley to thereby combine said components to determine range rate, an indicator connected with said movable pulley and movable therewith along one coordinate, a chart-carrying drum operatively associated with said indicator and movable along another coordinate, and input means for moving said drum relative to said indicator to establish average shell velocity for a given advance range.

2. In a fire control system, means to compute sight deflection comprising mechanisms to obtain the cross components of own ship and target speeds, adjusting means for said mechanisms including follower members, a chart-carrying drum movable along one coordinate and an indicator associated with said drum and movable along another coordinate, a drive for said drum, gearing for operating said indicator, an input shaft coupled to said gearing for operating the same to move said indicator, a drift cam also driven by said shaft and having a follower, and a flexible element having one end connected to the drive for said drum and its other end connected to said follower, with intermediate portions thereof operatively connected to the first named follower members.

3. In a fire control system, means to compute sight deflection comprising mechanisms to obtain the cross components of own ship and target speeds, adjusting means for said mechanisms including follower members, a chart-carrying drum movable along one coordinate and an indicator associated with said drum and movable along another coordinate, a drive for said drum, gearing for operating said indicator, an input shaft coupled to said gearing for operating the same to move said indicator, a drift cam also driven by said shaft and having a follower, wind correction means including a follower member, and a flexible element having one end connected to the drive for said drum and its other end connected to said drift cam follower, with intermediate portions thereof operatively connected to the first and last named follower members. 4. In a fire control system, means to compute sight deflection comprising mechanisms to obtain the cross components of own ship and target speeds, adjusting means for said mechanisms including follower members, a chart-carrying drum movable along one coordinate and an indicator associated with said drum and movable along another coordinate, a drive for said drum, gearing for operatin said indicator, an input shaft coupled to said gearing for operating the same to move said indicator, a drift cam also driven by said shaft and having a follower, a second drum for carrying a sight deflection spot chart and operatively connected to said input shaft, an indicator associated with said second drum and including a follower member, and a flexible element having one end connected to the drive for the first named drum and its other and connected to said drift cam follower, with intermediate portions thereof operatively congected to the first and last named follower memers.

5. In a fire control system, means to compute sight deflection comprising mechanisms to obtain the cross components of own ship and target speeds, adjusting means for said mechanisms including follower members, a chart-carrying drum movable along one coordinate and an indicator associated with said drum and movable along another coordinate, a drive for said drum, gearing for operatin said indicator, an input shaft coupled to said gearing for operating the same to move said indicator, a drift cam also driven by said shaft and having a follower, wind correction means including a follower member a second drum carrying a sight deflection spot chart and operatively connected to said input shaft, an indicator associated with said second drum and including a follower member, and a flexible element having one end connected to the drive for the first named drum and its other end connected to said drift cam follower, with intermediate portions thereof operativel connected to all of said follower members.

6. In a fire control system, means to compute drum including a follower member, means operatively connecting said input shaft to said sec ond drum, a third drum carrying a spot range chart and operatively connected to said second drum, a fourth drum carrying a sight angle chart and operatively connected to said second and third drums through said input shaft, and a flexible element having one end connected to the drive for the first named drum and 10 its other end connected to 'said drift cam fQllower, with intermediate portions thereof operatively connected to all said follower members. EARL E. LIBMAN. 

